Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. Emulsion aggregation toners may be used in forming print and/or xerographic images. Emulsion aggregation techniques may involve the formation of a polymer emulsion by heating a monomer and undertaking a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210, 5,994,020, and U.S. Patent Application Publication No. 2008/0107989, the disclosures of each of which are hereby incorporated by reference in their entirety.
Polyester toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Patent Application Publication No. 2008/0153027, the disclosure of which is hereby incorporated by reference in its entirety. The incorporation of these polyesters into the toner requires that they first be formulated into emulsions prepared by solvent containing batch processes, for example solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE), which is both time and energy-consuming. In both cases, large amounts of organic solvents, such as ketones or alcohols, have been used to dissolve the resins, which may require subsequent energy intensive distillation to form the latexes.
Solventless latex emulsions have been formed in either a batch or extrusion process through the addition of a neutralizing solution, a surfactant solution and water to a thermally softened resin as illustrated, for example, in U.S. Patent Application Publication Nos. 2009/0208864 and 2009/0246680, the disclosures of each of which are hereby incorporated by reference in their entirety. However, certain amorphous resins may be difficult to process without the use of a solvent in that they do not exhibit a sharp melting point and even at 100° C., exhibit substantial viscosities which may work against the formation of emulsions. In addition, certain amorphous resins are more susceptible to molecular weight degradation in the solvent-free process on account of their composition.
Solvents may be added to amorphous resins to reduce the viscosity and permit necessary reorientation of chain end, which may stabilize and form particles which lead to the formation of stable latexes. The additional process step of distillation to remove the solvent is, however, not desirable, as it adds complexity, energy consumption and cost.
It would be advantageous to provide a more efficient solvent-based process for the preparation of a polymer latex, particularly latexes formed from high molecular weight amorphous resins that degrade through other emulsification processes, suitable for use in a toner product that has a high product yield.